1. Field of the Invention
The present invention relates to a recyclable resin-scaled type semiconductor device. For example, a semiconductor element mounted on a lead frame is sealed with thermoplastic resin.
2. Description of the Related Art
Semiconductor devices covered by thermosetting resin may be manufactured according to the following method.
A semiconductor element bonded on a lead frame is disposed in a cavity defined by mold. The semiconductor element is interconnected with a lead frame by bonding wires comprised of a conductive material (Cu, Fe--Ni alloy). The cavity has a gate that casts the thermosetting resin into the cavity.
The epoxy resin (thermosetting resin) is cast from the gate. The epoxy resin is heated to the molding temperature by heating the mold, and the epoxy resin hardens. The epoxy resin seals the semiconductor element, the bonding wires, and a part of lead frame. The hardened resin is called a Package. Finally, the mold cools below the molding temperature of the epoxy resin.
As mentioned above, in fluidity and adhesion point of view, the thermosetting resin is applied to manufacturing the semiconductor devices.
About 60 seconds average is required for hardening the thermosetting resin, because of the step of cooling the mold. The required hardening time decreases the productivity of the semiconductor devices.
Further, generally speaking, the thermosetting resin has high fluidity, this characteristic is the cause for easily generated flashes.
Further, the package cannot be recycled because the heat-treated thermosetting resin doesn't have fluidity as before. Thus, unused packaging material must be dumped into a land fill, Unused material results from dividing the semiconductor element from the element board, dividing the package from the semiconductor element, and destroying the package by fire.
If a thermoplastic resin is substituted for the thermosetting resin, about 10 seconds average is required for hardening the thermoplastic resin. The thermoplastic resin can also be recycled because fluidity returns after heat-treating. Thus, waste material may be advantageously reclaimed and reused.
The thermoplastic resin, however, has a lower adhesion than the thermosetting resin. This characteristic allows moisturized air to enter into the semiconductor device through the interface between the package and the lead frame. It is the problem of moisture proof (or wet endurance). Therefore, thermoplastic resin has not been used.